In optical transmission, for relaying, amplification, and the like, it is necessary to optically connect optical fibers together or an optical fiber to a light-emitting device, a light-receiving device, an amplifier, or the like. Such an optical connection is realized by butting the end faces of optical fibers together or the end face of the optical fiber and the light-receiving (or light-emitting) face of such a device against each other.
For example, regarding optical connectors, various kinds of techniques have been proposed concerning the method of processing and fixing the front end face of an optical fiber. The method of making an optical connector disclosed in Japanese Patent Application Laid-Open No. 7-306,333 describes a method for rounding corners in a front end portion of an optical fiber by heat treatment, the chemical processing with an acid or the like, and physical processing with abrasive grains. Also, the method of processing an end face of an optical fiber disclosed in Japanese Patent Application Laid-Open No. 55-138,706 is a method in which the end face of the optical fiber is heated by discharge such as to yield a roundness with a radius not smaller than the radius of the optical fiber. These documents, however, do not disclose any specific technique for fixing an optical fiber to an optical connector.
The method of making an optical connector disclosed in Japanese Patent Application Laid-Open No. 58-108,507 employs a technique in which, after a front end face of a cut optical fiber is melted so as to become smooth, the optical fiber is inserted into the core of the connector and secured therein with an adhesive. Here, the position to secure the optical fiber is where the tip of the optical fiber and the tip of the core substantially match each other. In the matching process, the optical fiber is moved and positioned such that the tip of the optical fiber is disposed at the same position as the front end face of the core or slightly inside thereof, while being observed through a microscope or by placing a planar jig made of a material softer than the optical fiber at the tip of the core.
On the other hand, the optical connector disclosed in "Fiber PC Optical Connector" in NTT R&D vol. 45, No. 6 (1996), pp. 95-100 employs a method in which an optical fiber subjected to end-face processing for chamfering the cleavage plane thereof is fixed such as to project from an end face of a ferrule. The amount of projection is a value at which, in a connected state, the optical fiber is buckled by a pressure. It aims at maintaining a contact pressure by buckling. Consequently, a space for allowing the optical fiber to flex is secured within the ferrule.